KDVD: Why this Artifact?

Prodater64 · #1 09-20-2005, 07:14 AM

How call you it?
What is the reason?

HC Encoder.
Present in 2pVBR and CQ_Maxbitrate modes.
Doesn't matter if LRemoveDust_YV12 or Removegrain + Deen used, it is present anyway.

Dialhot · #2 09-20-2005, 07:50 AM

How did you take your snapshot ?
Because I often have this kind of things but this is a player problem. The artifact is not in the video.

GFR · #3 09-20-2005, 11:07 AM

You mean the ringing next to the sharp transition to the black borders? That's Gibbs or ringing.

Does the original show some ringing?

Does it happen without any filtering, or with other encoders?

Are the black borders part of the picture or are they introduced by the player?

If they are part of the picture and the ringing is induced by filtering, make sure you are filtering before adding the borders.

If the ringing is a product of the encoding you need to have less quantization in the high frequencies (try a different matrix or different settings.

Make sure you crop at an integer number of blocks.

Hope it helps.

Boulder · #4 09-20-2005, 11:58 AM

You can often see that where the film pixels end and borders begin. Usually the borders are not mod-16 in size so a macroblock contains a sharp edge between the black and non-black material. That's why that ringing occurs.

Prodater64 · #5 09-20-2005, 01:51 PM

Quote:

Originally Posted by GFR

...
Does the original show some ringing?

Yes, the original show same artifact.

GFR · #6 09-20-2005, 02:20 PM

GIGO = garbage in garbage out

If the source is bad, there's a natural tendency that it gets worse. It's a law of nature.

Try cropping out the artifact (at the next block boundary), or using some kind of deringing filter (you may find it difficult to get good deringing - YMMV).

Boulder · #7 09-20-2005, 03:03 PM

Quote:

Originally Posted by GFR

or using some kind of deringing filter (you may find it difficult to get good deringing - YMMV).

And in this case, deringing should be applied only to the areas that are close to the borders. IMHO it's much better to crop a few more pixels off than blur the whole image with deringing - which will never remove the problem completely without destroying all the details elsewhere.